fix: fight restart bug, mobile TTS, character sizing, bitcoin symbols

- Fix fight replay showing empty scene: validate rounds before playing,
  retry loading fight data up to 5 times when rounds are missing
- Add COOP/COEP headers to production server for SharedArrayBuffer
  (required by Kokoro TTS WASM threading on mobile)
- Add blob: to scriptSrc/workerSrc CSP for Web Worker support
- Fix mobile character cutoff: raise ground line to 0.82, add
  MOBILE_SCALE_CAP (0.55) so fighters never shrink too small
- Add ₿ bitcoin chest badge to all fighter sprites (scales with tier)
- Add sats coin stack on bot profile page proportional to satsWon
- Seed dev tournament with 8 mock bots on startup (dev mode only)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/game/FightScene.ts

@@ -9,7 +9,7 @@ import { pickChoreography } from './fight/choreography/picker'
 export { pickChoreography }
 import {
   isPerfMode, perfParticles, isReducedMotion, haptic,
-  GROUND_Y_RATIO, HOME_A_RATIO, HOME_B_RATIO, REFERENCE_HEIGHT, SPRITE_LOAD_TIMEOUT_MS,
+  GROUND_Y_RATIO, HOME_A_RATIO, HOME_B_RATIO, REFERENCE_HEIGHT, MOBILE_SCALE_CAP, SPRITE_LOAD_TIMEOUT_MS,
   FIGHTER_BASE_SCALE, FIGHTER_TIER_SCALE, JUDGE_SCALE, HUMAN_COACH_SCALE, HUMAN_RUN_SCALE,
   AMBIENT_PARTICLE_COUNT, SKY_GRADIENT_BANDS, GROUND_DEPTH_LINES, PERSPECTIVE_GRID_LINES, PILLAR_WIDTH,
   SPEECH_BUBBLE_MAX_CHARS, SPEECH_BUBBLE_WRAP, SPEECH_BUBBLE_MAX_LINES, SPEECH_BUBBLE_FONT_SIZE, SPEECH_BUBBLE_DEFAULT_DURATION,
@@ -193,7 +193,7 @@ export async function createFightScene(config: FightSceneConfig) {
   const vhsTracking = (duration: number = 0.4) => _vhsTracking(fightCtx, duration)
   const dimensionalShift = (duration: number = 0.6) => _dimensionalShift(fightCtx, duration)
 
-  const SF = Math.min(1, H / REFERENCE_HEIGHT)
+  const SF = Math.max(MOBILE_SCALE_CAP, Math.min(1, H / REFERENCE_HEIGHT))
   const GROUND_Y = H * GROUND_Y_RATIO
   const HOME_A = W * HOME_A_RATIO
   const HOME_B = W * HOME_B_RATIO